The present invention relates generally to an environmental control unit for use in air handling systems that provides air conditioning, heating, and high efficiency airborne toxic agent filtration equipment and functions in a single unitary packaged unit, and, in particular, relates to a unitary packaged unit providing heating, ventilation and/or air conditioning of an air supply provided to an enclosure as well as protecting the occupant(s) and equipment in the enclosure against external or internal airborne release of toxic chemical, biological, or radiological agents that threaten to contaminate the air supply. It also relates to an air handling method and system providing CBR filtering for the airspace of a shelter or safe room.
There is an ever-increasing need for air handling systems that include air filtration systems that can be deployed to protect an enclosure against noxious airborne agents released in the vicinity of the enclosure. Every year there are numerous incidents of noxious fumes entering buildings and causing illness and disruptions due to accidents or malicious pranks. There now is heightened concern about super-toxic airborne agents being released as part of a nuclear, biological or chemical (xe2x80x9cNBCxe2x80x9d) attack launched by terrorists in a metropolitan area or as directed against a particular governmental, public or private building or structure. In addition, military personnel in combat areas may need protection from enemy releases of airborne chemical, biological, and radiological (xe2x80x9cCBRxe2x80x9d) agents in the vicinity of a tent or other enclosure area where the troops are bivouacked or have set up a field command or field hospital, and so forth. Whether a civilian or military setting, a typical air handling system for an enclosure will be served by ductwork connecting airflow between the enclosure and a remote HVAC (xe2x80x9cheating, ventilating, and air conditioningxe2x80x9d) unit. The HVAC system is normally used to adjust the temperature of the airflow and circulate the air to and from one or more enclosures.
Standard dust filters are ineffective against CBR agents. Standard dust filters, such as cardboard framed fiberglass matt filters, have relatively low efficiency rates for removing for dust and particles, and are not useful for removing pollen, microorganisms, smoke, or gases. Commercially available electrostatic fiber filters have higher efficiencies than standard dust filters and can remove pollens and other small solid particulates, but they can not intercept and remove gases. HEPA (xe2x80x9cHigh-Efficiency Particulate Airxe2x80x9d) filters are known that are used for high-efficiency filtration of airborne dispersions of ultrafine solid and liquid particulates such as dust and pollen, radioactive particle contaminants, and aerosols. For example, for removal of non-toxic aerosols, HEPA filters are typically used as the sole filtration element. The efficiency of a HEPA filter is standardized as being at least 99.97% for particles of dioctylphthalate (DOP) having a size of 0.3 microns in diameter. The airflow resistance of conventional HEPA filters is typically about one (1) inch, water gauge (iwg) at 500 feet per minute (FPM) approach velocity. This resistance increases steadily as the HEPA filter loads with dust or other fine particles in service. However, where the threat is a gaseous chemical compound or a gaseous particle of extremely small size (i.e.,  less than 0.001 microns), the conventional commercially-available HEPA filters can not intercept and control those types of airborne agents. In addition, the vast majority of prior air handling systems have not been designed nor were designable to accommodate the large increase in airflow resistance that would be associated with use of a conventional HEPA filter.
The most commonly found filter technology used to filter gaseous substances and materials from an airflow is based on activated carbon. CBR filtering has been previously implemented in certain applications, such as in gas masks or in industrial processes, by using filter beds of activated impregnated carbons or other sorbents for ultra-high-efficiency filtration of super toxic chemical vapors and gases from an air or gas stream passed through the filter. Commercial filters of this sort generally include activated carbon loaded nonwovens, in which the activated carbon is bonded to a nonwoven fiber mat. Carbon filters used for protection against toxic chemicals are typically designed to maintain an efficiency of at least 99.999% removal of airborne particulates. An activated carbon filter typically functions by removing molecules from an air stream by adsorption in which molecules are entrapped in pores of the carbon granules. Activated carbon is an effective sorbent for removal of a wide range of chemical vapors due to its extensive microporosity and broad range of pore sizes. In order to filter high vapor pressure chemicals, impregnants are added to the activated carbon. The impregnants react with the gas passing through the filter to form products that are captured by the filter or rendered innocuous. The pressure drop of high-efficiency carbon filters may range from about 1 to 6 iwg at 250-500 FPM approach velocity. These carbon filters also have been used in combination with a HEPA filter.
Activated carbons are useful in respirators, collective filters and other applications, and often involved the use of special impregnates to remove gases that would not otherwise be removed through the use of unimpregnated activated carbons. These impregnated activated carbon adsorption for removal of toxic gases and/or vapors have been known and used for many years. The prior art formulations often contain copper, chromium and silver impregnated on an activated carbon. These absorbents are effective in removing a large number of toxic materials.
For example, it is known that removal of highly toxic chemicals such as cyanogen chloride, hydrogen cyanide and cyanogen can be achieved with the presence of chromium and copper on the activated carbon. Copper and silver impregnants have been shown to be effective in the removal of arsine and phosphine. Chlorine, hydrogen chloride, hydrogen fluoride and hydrogen sulfide are also removed by the presence of copper impregnants on activated carbon.
In addition to a number of other inorganic materials, which have been impregnated on activated carbon, various organic impregnants have been found useful in military applications for the removal of cyanogen chloride. Examples of these include triethylenediamine (TEDA) and pyridine-4-carboxylic acid. In the nuclear industry, the impregnation of charcoal absorbents with triethylenediamine (TEDA) has led to an improved adsorbent with excellent performance in the monitoring and trapping of radioactive iodine and methyl iodide from the off-gases of nuclear reactors The same technology has been extended to the treatment of military charcoal used in respirators for improved protection against small, volatile super-toxic compounds, such as cyanogen chloride, which normally do not adsorb on the charcoal surface to any significant extent.
Various types of high-efficiency filter systems, both commercial and military systems, have been proposed for building protection using ASZM-TEDA carbon for filtering a broad range of toxic chemical vapors and gases. These filter systems have been proposed for integration into the HVAC system of new construction. However, conventional air handling units are not designed to accommodate a large increase in airflow resistance that an activated carbon filter would add. In addition, conventional air handling units have dust filter slots that permit relatively high bypass around the filter media, which not only reduced the overall efficiency of the HEPA filters but also is unacceptable where toxic airborne agents must be entrapped.
FIG. 1 illustrates a conventional HVAC system 100 having limited CBR (xe2x80x9cchemical, biological and radiologicalxe2x80x9d) filtering capability. An air intake/blower unit 11 incorporates a CBR filtration apparatus. Ideally, such a system would establish a toxic-free area (xe2x80x9cTFAxe2x80x9d) for the occupants in the interior space 17 of enclosure 12 where they would be protected from the CBR threat 16 and could breath the air inside the enclosure without need of a gas mask. As illustrated, the interior space 17 of the enclosure 12 receives and returns air from HVAC unit 10 via ducts 13 and 14, respectively. The returned enclosure air 14 is combined with intake air 18 introduced via the intake/CBR filtering unit 11 to provide combined airflow stream 15 that is inputted to the HVAC unit 10. If more than one outside air intake is used, a separate CBR filtration unit is dedicated to each respective intake.
Consequently, the conventional CBR filtration units have been used as stand-alone units that filter only the outside inlet air, and not the air already in the system, because it was impractical to engineer them to handle the primary airflow in the HVAC system. Conventional CBR filtration unit designs create significant pressure drops in any meaningful airflow passed through them. Therefore, the previous air handling systems providing CBR filtration capability required that a bulky and heavy HVAC unit and a separate CBR filtering/intake unit be transported and installed with all the ductwork needed to support such a system.
The conventional air handling system also has a serious design flaw in that internal CBR contamination events are not resolved. That is, there is no provision for eliminating super-toxic agent contamination of the primary airflow stream being circulated through the system to and from enclosure 12. To reduce the possibility of contaminated outside air infiltrating the interior space 17 of enclosure 12 due to leakage or temporary openings of a door or tent flap to the enclosure, air is introduced into the enclosure 12 at a rate sufficient to produce an overpressure or positive pressure in the airspace 17 of enclosure 12 to create an outward flow of air through any opening(s) in the enclosure 12. To create the positive pressure inside the enclosure, the supply airflow rate to the interior space 17 of the enclosure 12 must exceed the exhaust airflow rate. Toxic-free area enclosures are often designed for a minimum overpressure goal of 5 Pa (0.02 inches water gauge (iwg)). This overpressure corresponds to a wind speed impact pressure normal to a wall of 12 km/hr (7 mph), which is the wind speed condition generally considered to be the most favorable for directing a plume of agent with minimum dispersion toward and outside air intake.
Despite these overpressure measures, the problem is that wind gusts or nearby explosive blasts, or repeated or extended openings of the door/tent flap by occupants, can exceed the overpressure capabilities of a given air handling system. Alternatively, a contaminated person may be brought inside the enclosure for treatment and so forth having volatile or air-dispersible traces of the super-toxic agent contaminating his or her body, clothes or equipment. In the conventional air handling system 100, the CBR filter only decontaminates intake air 18, not the primary airflow 13 being recirculated internally throughout the HVAC system.
Consequently, if and when the air being recirculated within system 100 becomes contaminated, the enclosure 12 can not be maintained in or returned to toxic-free state because the contaminated air will not be effectively removed to a safe level by merely passing it through conventional dust filters, or HEPA filters for that matter if the HVAC unit somehow can tolerate high airflow resistance, installed to filter the main air flow stream in a conventional HVAC unit.
As indicated above, the CBR filtering is restricted to the outside air intake stream in the HVAC ventilation system. In some conventional designs, the rate of intake air introduced is approximately 10% the total volume of air in the system 100. In that scenario, air is only CBR filtered upon introduction into the system, but not during subsequent recirculation cycles in the system 100.
To remove chemical, biological, and radiological agents from air in an environmental space, it has been proposed to use a packed bed of activated carbon, such as using a construction as generally described above. However, with conventional carbon filter schemes, this has the significant drawback of creating a very substantial pressure drop across the packed bed, i.e., the packed bed requires a tremendous pressure force to push the air stream through the packed carbon. The implication of this is that very powerful air handling equipment is required, typically much more powerful than the typical air handling equipment in use at most large buildings or used to serve a large military tent. Therefore, it has not been economically or physically practical to incorporate air handling capability into such HVAC systems that could support CBR filtering of the main flow air.
There is a heightened need for a way of protecting a building or other enclosure against nuclear, biological, and chemical agent attacks, as well as providing a counter-measure to neutralize any internal contamination events. The present invention addresses and solves the above-mentioned problems and shortcomings.
The environmental control unit (xe2x80x9cECUxe2x80x9d) of the present invention is a unitary packaged unit suited to provide air conditioning, heating, and CBR filtering protection needs for an enclosure. The enclosure or enclosures that is (are) served by the ECU are expected to be occupied by a person or persons and/or sensitive equipment, and so forth, needing protection from contamination by toxic airborne or air-dispersible agents in addition to any needs for general air handling support.
In one embodiment of the invention, there is an environmental control unit, comprising, as a unitary packaged unit for rapid deployment in the field or for use in an existing structure, a means adapted to receive air conducted via ductwork to the control unit from an enclosed space that is being protected and provided air handling support by the ECU. An air intake blower adapted for intake of a stream of external air into the control unit is included along with means for combining the intake air and air received from the enclosed space to provide an air stream. An important feature is that a filter apparatus adapted to remove CBR agents from the air stream is integrated into the ECU. The CBR filter apparatus used is capable of decontaminating the air stream of CBR agents without rapidly blinding or otherwise unduly interfering with the air stream while traversing the unit. More directly it effectively removes chemical, biological and/or radiological agents without excessive pressure drop in air flow. Due to the usage of high performance CBR filtering apparatus components, it is possible to integrate and employ HVAC components into the same unitary packaged unit to meet the air handling requirements without encountering undue weight or bulk issues that otherwise would frustrate incorporation of CBR filtering means and functionality into the same unit.
The ECU of the present invention also includes a temperature adjustment means for manipulating the temperature of the air stream, before or after the CBR filtering, as well as means adapted for outputting the filtered, temperature-manipulated air stream for conduction of the filtered, temperature-manipulated air stream back to the enclosed space with creation of a positive air pressure in the enclosed space, and a primary air stream blower adapted to draw the air stream into the receiving means and discharge the filtered and heated/cooled air stream from the outputting means.
As such, the ECU can be used to sustain a comfortable breathable atmosphere within a given enclosure for short or prolonged durations of time while protecting occupants or items located therein from contamination by toxic airborne agents. In particular, the ECU protects occupants of the enclosure against external and/or internal airborne release of super-toxic chemical, biological, or radiological agents, while concurrently providing HVAC function.
In one embodiment, the CBR filtering component is incorporated into the HVAC""s primary or main air flow stream, such that the entire air stream, and not merely the air intake, receives intermittent, supplemental and continued CBR filtration while being recirculated through the air handling system including the enclosure""s air space. The ECU can be implemented to protect and condition the air space within temporary, semi-permanent or permanent structures or buildings. These structures can be stationary or mobile. These structures include tents, office buildings, residential homes, mobile homes, RV""s, or other structures or buildings in which partitions or walls define an enclosure in which internal air is separated from external air. The term xe2x80x9cexternalxe2x80x9d refers generally to locations outside the enclosure being protected by the ECU, which could be a location in the elements outside the building or structure containing the enclosure, or, alternatively, a location within the same building but outside the enclosure.
In one implementation, the ECU is located outside the structure having an enclosure for which air is protected/decontaminated by the ECU. In another implementation, the ECU is located inside a structure including an enclosure (e.g., a so-called xe2x80x9csafe roomxe2x80x9d) to be protected by the ECU. In the latter scenario, the ECU can be installed as a stand-alone air handling unit for the enclosure, or, alternatively, it can be integrated with a standard HVAC system provided for air handling in the structure. The ECU can be located inside the xe2x80x9csafe roomxe2x80x9d itself or in a separate area within the building with air tight ductwork installed that extends between the ECU and the safe room. In one arrangement, when a CBR threat is detected, the enclosure to be protected will have its air space and air handling system isolated from the standard HVAC system via damper control so that the ECU handles all its air handling needs. Alternatively, the enclosure could be maintained as a full time xe2x80x9csafe roomxe2x80x9d in which the safe room""s enclosure""s air space is kept isolated from the rest of the air space within the building, and the ECU is used continuously or as needed to support the air handling needs of the safe room. In a further embodiment, the ECU used to protect the air of a safe room includes a CBR filtering system, but not an air conditioning or heating system. This is practical because air drawn from outside the safe room but inside the building into the ECU equipped with a CBR filtering system but not an A/C system, can be air conditioned or heated by the separate HVAC system used to handle the air generally inside the building.
For facilities that require continuous operation during a short duration threat with little or no warning, such as a terrorist attack, continuous filtration of the ventilation air intakes should be employed. A CBR system is provided to resist the short duration penetration of agents into a toxic-free area (TFA) where occupants can function without individual protective equipment, a CBR filtration system. For longer term events or where ingress/egress of the enclosure occurs during the event, the CBR filtration system can be provided to provide an overpressure that helps prevent the penetration of agents through the TFA envelope.
In one embodiment of the present invention, the filter apparatus component of the ECU has a design adequate for providing high-efficiency, single-pass filtration of gas phase contaminates, including super-toxic chemical, biological, and radiological agents. In one embodiment, a framed filter includes activated carbon deployed in one or more layers through which the air stream is directed. In one aspect, the filter apparatus generally includes a filter housing having an inlet opening and an outlet opening to permit air to flow in through the inlet opening, through the housing and out through the outlet opening.
The ECU of the present invention can remove chemical war agents, including, for example, mustard (blister agents); sarin (nerve agents); phosgene (choking agents); and cyanogen chloride (blood agents); anthrax (bacterial agents), smallpox (viral or pathogenic agents); as well as industrial pollutants or other toxic agent threats released by accident or act of terrorism, soon after they are introduced into the ventilation system and when recirculated back through the HVAC unit. The ECU can be used as a military, commercial or with a residential HVAC system; an over-pressurization system; and/or a negative air isolation system, which provides highly efficient CBR filtration without causing undue airflow resistance.